supply line of Xuzhou. The Yan forces arrived at the Sui River on 14 April, and settled across the river facing the government camp. A battle broke out on 22 April in which the government forces led by Xu Yaozu were victorious. As the government forces had victories one after another, the military morale of the Yan forces started to plummet. Soldiers of the Yan forces were mostly from the north, and they were unaccustomed to the heat as summertime approached. The generals of Zhu Di proposed a withdrawal to regroup, which Zhu Di rejected. During this time, the imperial court received rumours that the Yan forces had retreated back north. Jianwen Emperor recalled Xu Yaozu back to Nanjing, which reduced the government strength north of the Yangtze River. On 25 April, the government forces moved the camp to Lingbi and began to set up fortifications. A series of battles ensued, and the government forces gradually ran out of food supply as the Yan forces successfully blocked their supply line. With the imminent shortage of food supply, the government forces planned to break out of Yan encirclement and regroup in the Huai River. The break out signal was decided as three shots of cannon fire. On the next day, the Yan forces happened to attack Lingbi fortification with the same signal. The government forces completely collapsed in a state of confusion as the Yan forces stormed to take over and ended the battle. The main strength of the government forces was crushed decisively in the Battle of Lingbi, and the Yan forces were now unmatched north of the Yangtze River. Fall of Nanjing After the Battle of Lingbi, the Yan forces advanced straight toward the southeast and captured Sizhou on 7 May. Sheng Yong attempted to set up a defensive line on the Huai River to prevent the Yan forces from crossing. As the attack was halted in Huai’an, Zhu Di divided the army and launched a converging attack on Sheng Yong. Sheng Yong was defeated, and the Yan forces captured Xuyi. On 11 May, the Yan forces marched toward Yangzhou, and the city surrendered one week later. The nearby city of Gaoyou also surrendered soon after. The fall of Yangzhou was a devastating blow for the government forces, as the imperial capital Nanjing was now exposed to a direct attack. After discussing with Fang Xiaoru, the Jianwen Emperor decided